We have been studying the role that protein degradation plays in regulating cell growth control, through the study of a mutant defective in protein degradation, the E. coli lon mutant. This strain is defective in cell division regulation after DNA damage; we have demonstrated that this defect is due to accumulation of a highly unstable cell division inhibitor, the product of the SulA gene. In addition, we have shown that, in vitro, the SulA gene is transcribed from a single promoter which is repressed by the LexA repressor, as part of an integrated response to DNA damage known as the SOS system. 1on mutants also overproduce capsular polysaccharide, and we have developed a system for the simple assay of the regulation of the genes necessary for capsule synthesis (cps), using cps-lac operon fusions. Using these strains, we have isolated and mapped mutations in two previously unknown genes which regulate capsule synthesis (cpsR and cpsS). Further work will concentrate on the interaction of 1on, the cps regulators, and the structural genes which are regulated.